This invention relates generally to high frequency amplification devices and more particularly to such a device where amplification results from the interaction of electron beams with RF fields in a wave propagating transmission line.
Interactive types of devices for amplification of RF signals at microwave frequencies are well known. The traveling wave tube constitutes such a device and is one in which a longitudinal electron beam interacts continuously with the RF field of a wave traveling along a wave propagating slow wave circuit structure such as a helix. Additionally, means are provided to couple an external radio frequency (RF) signal to and from the slow wave circuit structure. The velocity of the electron stream, moreover, is adjusted to be approximately the same as the phase velocity of the wave on the helix. When an RF wave is launched on the slow wave circuit, i.e. the helix, the longitudinal component of the field interacts with the electrons traveling along in approximate synchronism with it. Some electrons will be accelerated while others will be decelerated which results in a progressive rearrangement in phase of the electrons with respect to the wave. The electron stream thus modulated in turn induces additional waves on the helix. This process of mutual interaction continues along the length of the helix with the net result being that direct current energy is given up by the electron in the stream to the circuit as radio frequency energy and the RF signal is thus amplified.
One example of a traveling wave tube is shown and described in U.S. Pat. No. 3,760,219, issued to Charles M. DeSantis, et al. one of the present inventors, on Sept. 18, 1973, and discloses, among other things, a traveling wave tube having a control grid for effecting klystron type of bunching of the electron stream. Another known type of microwave amplification device, which employs a transverse field interaction for its operation, comprises a multibeam klystron which has been disclosed and described, for example, in a U.S. Army ECOM technical report entitled, "High Power Traveling Wave Multiple Beam Klystron", Branch, et al. ECOM-007F technical report, October, 1967, D.A. 28-043AMC-00007(e). There two and three waveguide multiple beam klystron structures are shown and described that produce megawatts of power over a wide frequency band and at substantially lower beam voltages relative to single beam conventional klystrons. The multiple beam klystron utilizes a multiplicity of separate and distinct electron beams that are arranged to interact with RF fields in at least two or more waveguides that are periodically loaded with capacitive gaps consisting of both buncher and catcher type gaps. The buncher gaps are driven by a transverse RF wave traveling in one waveguide where the wave in turn modulates each of the beams. The beams then travel across the buncher gaps in the other waveguide where an amplified RF wave is induced therein and which is conveyed to an output circuit.
Accordingly, it is an object of the present invention to provide an improvement in apparatus for amplifying electromagnetic waves.
It is another object of the invention to provide an improvement in apparatus for amplifying microwave signals.
It is a further object of the invention to provide an improvement in microwave amplification devices which operate on the principle of field interaction between an electron beam and an RF signal wave.
It is yet another object of the invention to provide an improvement in field interaction amplification devices which results in improved signal gain and efficiency.